[CI/CD] Update Docker image build script syntax in packaging pipeline

Author: lithorus

.github/workflows/packaging-pipeline.yml

@@ -160,7 +160,7 @@ jobs:
           echo "BUILD_ID=$(ci/generate_version_number.py)" >> ${GITHUB_ENV}
 
       - name: Build Docker image
-        run:
+        run: |
           export OPENCUE_PROTO_PACKAGE_PATH="${{ needs.build_opencue_packages.outputs.opencue_proto_path }}"
           export OPENCUE_PYCUE_PACKAGE_PATH="${{ needs.build_opencue_packages.outputs.opencue_pycue_path }}"
           export OPENCUE_PYOUTLINE_PACKAGE_PATH="${{ needs.build_opencue_packages.outputs.opencue_pyoutline_path }}"